A curious situation: Black cannot remove the pieces from the queenside, but White still cannot attack them. Both sides, therefore, prefer to advance pawns on the other side of the board. A possible plan for White is to advance his majority on the kingside and distract Black's pieces to finally capture the a2-knight.
20... a8a7  21. b7f3 Nepomniachtchi's preparation probably ended around here. With a pawn for the exchange and still all the plusses mentioned earlier. White has the advantage. 21... a7c7  22. f3e2  22... h7h6 